Unveiling the K1 (1270) double-pole structure in the B ¯ →j /ψρ K ¯ and B ¯ →j /ψ K ¯ ∗π decays

By looking at the pseudoscalar-vector meson spectra in the B¯→J/ψρK̄ and B¯→J/ψK̄∗π weak decays, we theoretically investigate the double-pole structure of the K1(1270) resonance by using the chiral unitary approach to account for the final-state interactions between the pseudoscalar (P) and vector (V) mesons. The K1(1270) resonance is dynamically generated through these interactions in coupled channels and influences the shape of the invariant mass distributions under consideration. We show how these shapes are affected by the K1(1270) double-pole structure to confront the results from our model with future experiments that might investigate the PV spectra in these decays